Sheet like products such as facial tissues, napkins, paper towels, tissue paper, sheets of tin foil or wax paper, etc. are often packaged into individual packages having a stack of each product wrapped in a plastic wrapper. The machines that form the individual stacks of product often simultaneously form a set of stacks that are transversely offset from one another forming a plurality of lanes of stacks. These machines may interfold the sheets, fold the sheets with interfolding, form zig-zag sheets or even merely stack unfolded sheets.
Typically, the plurality of lanes is converted into a single file stream of stacks so that the single file stream of stacks can be passed through a wrapper. To form the single file stream of stacks, all of the stacks are typically deposited onto a discharge conveyor that deposits the stacks onto a wrapper in-feed conveyor that is a paddle style conveyor that extends at a right angle relative to the discharge conveyor. This arrangement is illustrated in FIGS. 25 and 27 of U.S. Pat. No. 7,364,398 assigned to the assignee of the instant application.
Unfortunately, this configuration has significant limits on speed. One particularly limitation is that the paddles must be far enough apart to allow the stacks to be fully positioned onto the wrapper in-feed conveyor while the paddles are moving. The paddle speed is equal to the paddle spacing multiplied by the number of packs per unit time. Further, it is highly preferred to have the paddle speed at less than 40 inches per second and a paddle spacing of at least 20 inches so to limit the amount of force that is applied to the stacks as they are engaged by the paddles. Unfortunately, this limits this type of transfer to 120 packs per minute or less.
A further problem with current pack wrappers is the ability to quickly and adequately cut the sleeve of plastic that surrounds the stack of product. Many prior art mechanisms for cutting the sleeve of plastic use complex cutting paths or complex machinery which are not suitable for making a high rate of cuts.
Finally, after the sleeve of plastic has been cut to form independent units of product that include a stack of product within a predetermined length of the plastic sleeve, the ends of the sleeve are open and need to be closed and then secured. Typically, this is done by again changing the direction of travel of the packs by 90 degrees using a sideways pusher and then passing the units through an apparatus that folds and then welds the open ends.
Unfortunately, the same problems discussed above apply to using a simple sideways push to change the direction of travel of the units by ninety degrees. Additionally, a reciprocal pusher mechanism further reduces the through put speeds due to the time required to get the pusher out of the way to receive the next unit in line.
There is therefore a need in the art for new and improved high speed wrappers and associated mechanisms and methods. The present invention relates to improvements over the current state of the art.